上下拖曳來換位ㄛ

左右滑動來刪除項目呦

要怎麼做啦

前一天做過了基本型的recyclervivew，那今天除了原本製作recyclerView所需的流程與元件以外，我們需要另外加入兩個東西，分別是
ItemTouchHelperCallback 跟 ITHelperInterface

1. ITHelperInterface.kt

interface ITHelperInterface {
    fun onItemMove(fromPosition:Int,toPosition:Int)   //處理用上下拖曳來產生換位效果
    fun onItemDissmiss(position:Int)                  //處理用左右滑動來刪除項目
}

2. ItemTouchHelperCallback.kt

class ItemTouchHelperCallback(var mAdapter: ITHelperInterface?): ItemTouchHelper.Callback() {

    override fun getMovementFlags(recyclerView: RecyclerView, viewHolder: ViewHolder): Int {
    
        //設定可往上及往下拖曳
        val dragFlags = ItemTouchHelper.UP or ItemTouchHelper.DOWN    
        //設定可往左及往右滑動
        val swipeFlags = ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
        //若不想要其中一個功能就改成ACTION_STATE_IDLE
        //val dragFlags = ItemTouchHelper.ACTION_STATE_IDLE          
        return makeMovementFlags(dragFlags, swipeFlags)
    }

    override fun isLongPressDragEnabled(): Boolean {
        return true
    }

    //設定item可滑動
    override fun isItemViewSwipeEnabled(): Boolean {
        return true                                         
    }

    //上下拖曳監聽事件
    override fun onMove(                                 
        recyclerView: RecyclerView,
        viewHolder: ViewHolder,
        target: ViewHolder
    ): Boolean {
        //呼叫ITHelperInterface的方法
        mAdapter!!.onItemMove(viewHolder.adapterPosition, target.adapterPosition)     
        return true
    }

     //左右滑動監聽事件
    override fun onSwiped(viewHolder: ViewHolder, direction: Int) {     
        //呼叫ITHelperInterface的方法
        mAdapter!!.onItemDissmiss(viewHolder.adapterPosition)           
    }
}

3. myAdapter

讓原先的Adapter繼承ITHelperInterface並且override裡面那兩個方法

class MyAdapter: RecyclerView.Adapter<BackpackAdapter.mViewHolder>(),ITHelperInterface {

    //........
    override fun onItemDissmiss(position: Int) {
        unAssignList.removeAt(position)
        notifyItemRemoved(position)
    }

    override fun onItemMove(fromPosition: Int, toPosition: Int) {
        Collections.swap(unAssignList,fromPosition,toPosition)
        notifyItemMoved(fromPosition,toPosition)
    }
}

4. MainActivity.kt

最後去Activity進行綁定啦

class MainActivity : AppCompatActivity() {

    val mAdapter = MyAdapter()
    
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_backpack)
        
        //這裡的recyclerview指的是你在activity_main.xml裡的recyclerview
        recyclerview.layoutManager = LinearLayoutManager(this)
        recyclerview.adapter = backpackAdapter

        val callback = ItemTouchHelperCallback(backpackAdapter)
        val touchHelper = ItemTouchHelper(callback)
        touchHelper.attachToRecyclerView(recyclerview)
        
    }
}

Done!